It has been known that .pi.-electron conjugated type polymeric compounds are transformed from semiconductors into conductors by partial oxidation or reduction and can be provided with an extremely high electroconductivity as that of organic compounds. Various kinds of .pi.-electron conjugated type polymeric compounds such as polyacetylene, polythiophene, polypyrrole, and polyhenylene have previously been developed and their applications have now been studied while utilizing their properties as a semiconductor and a conductor, and the properties of changing the electroconductivity by the dopant. Further, with recent progress in science and technology, demands have increased more and more for electronics display devices, batteries of high efficiency, and various kinds of sensors, and electroconductive polymers are expected to be capable of playing an important role in these fields.
Presently, many have sought to develop safe and convenient methods capable of providing electroconductive high polymers having higher electroconductivity, mechanical strength, and excellent circumstantial stability in any desired form, and preferably in the form of films which are advantageous for practical use.
It has been known that the .pi.-electron conjugated type polymeric compounds have excellent heat resistance due to their rigid molecular structures, and they are also expected to be substituents for metal materials such as for use in space aircraft, engineering plastics, and the like.
The recent progress in these technical fields can include the following.
For instance, Japanese Patent Laid-Open No. 89640/1983 discloses an electroconductive polyacetylene high polymer and Japanese Patent Laid-Open No. 47421/1981 discloses a linear poly(2,5-thienylene) polymer, a process for production thereof, and a semiconductor made of the produced polymer. Further, "J. Polym. Sci." by Kovacic, et al, vol. 18, (1980), page 2423+, or vol. 19, page 347+ disclose synthetic examples of polyparaphenylene, polyfuran and polyselenophene. Heretofore, the .pi.-electron conjugated type polymeric compounds as described above have been synthesized by using an oxidant such as sodium dichromate or a catalyst such as cuprous chloride and a nickel compound, or often prepared by pelletizing monomers and then applying a heat treatment at a high temperature.
As one of the methods of synthesizing the .pi.-electron conjugated type polymeric compounds other than those described above, there can be mentioned an electrochemical anodizing process. For instance, U.S. Pat. No. 3,574,072 discloses an example for the polymerization of a 5- or 6-membered heterocyclic compound, particularly, pyrrole, by means of electrochemical anodization. Further, "J. Chem. Soc. Chem. Commun." written by A. F. Diaz, page 635+ published in 1979, discloses that a film having an electroconductivity of less than 100 S/cm is formed by the anodizing polymerization of pyrrole in the presence of an electrolyte. The feature of the electrochemical anodizing method resides in that the resultant electroconductive high polymer can be obtained in the form of a film and that the amount of the dopant contained in the film can be controlled with ease and, accordingly, it is expected to be an effective method for obtaining an electroconductive polymeric film of relatively high electroconductivity.
However, examples of electroconductive high polymers obtained by the electrochemical anodizing process reported so far have been limited only to 5-membered heterocyclic polymers such as polypyrrole and polythiophene, as well as polyaniline, polypyridazine and polyphenylene.
Particularly, while polyphenylene has been noted from the early stages as an electroconductive high polymer, films having favorable properties have not yet been synthesized. For instance, "J. Polym. Sci., Polym. Chem. Ed." written by L. Rubinstein, vol. 21 (1983), page 3035+ discloses the synthesis of polyphenylene from a 2-phase solution of hydrofluoric acidbenzine by an electrochemical process and the properties thereof. Further, "J. Chem. Soc. Chem. Commun." written by K. Kaeriyame, 1984, page 1199+, discloses the synthesis of polyphenylene from a benzene solution containing aluminum chloride and various types of amine salts by an electrochemical process and the properties thereof. However, the electroconductivity of the polyphenylene films obtained by these methods is only within a range of 10.sup.-5 -10.sup.-4 S/cm, which is extremely low as compared with the values obtained by the pressure molding of powdery polyphenylene prepared by the conventional method, that is, a method of reacting benzene with an oxidizing agent shown in "J. Chem. Phys." written by D. M. Ivory, et al, vol. 71, (1979), page 1506+.
Furthermore, the .pi.-electron conjugated type polymeric compounds as described above and obtained by the conventional production process have often involved problems because they are significantly poor in moldability/workability due to their diminished ability to melt or dissolve, although they are excellent in heat resistance. Particularly, although electroconductive polymeric compounds such as polyparaphenylene, using a benzene or benzene derivative such as diphenyl as the monomer, cannot be obtained in the film-like state by the conventional method, advantageous properties have been expected therefor, such as electrode material for use in batteries at high efficiency. Accordingly, practical use of these electroconductive high polymers has not yet progressed at present.